Cutting Method for Inner Circumferential Face or Outer Circumferential Face of Work

ABSTRACT

A cutting method in which, in cutting an inner circumferential face or an outer circumferential face of a work based on turning of a main shaft around a predetermined position serving as a center, control is enabled to make a cutting velocity constant. To achieve the object, a cutting method is provided for an inner circumferential face or an outer circumferential face of a work, using a cutting tool projecting from a main shaft which turns around a predetermined position serving as a center and for which a turning radius is adjustable, wherein, in the case that a turning angular velocity of the main shaft is represented as ω, a distance from a turning center to a tip of the cutting tool is represented as R, and a cutting velocity of the tip of the cutting tool is set to a constant value C, making the cutting velocity of the cutting tool is made constant by performing control such that ω changes in association with a change in the distance R so that 
     
       
         
           
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     is formulated (where {dot over (R)} denotes a time differential of the distance R), thus providing an even cut face.

BACKGROUND OF THE INVENTION

The present invention relates to a cutting method for an innercircumferential face and an outer circumferential face of a work using acutting tool of a main shaft which turns around a predetermined positionserving as a center and for which a turning radius is adjustable, thecutting being performed by making a cutting velocity of the cutting toolconstant.

The “turning of the main shaft” is not limited to rotation of the mainshaft along a central axis thereof but refers to rotations includingrevolution of the main shaft around the predetermined position servingas a center.

What is called an orbit machining that a main shaft turns around apredetermined center has been adopted as a method for forming an innercircumferential face and an outer circumferential face of a work intocurved faces variously shaped like cylinders, tapered shapes, flanges,or the like, as disclosed in Patent Literature 1. This machining methodis technically advantageous in that machining can be achieved atwhatever position a table supporting the work is located.

A cutting velocity needs to be constant in order to provide an even cutface. However, for the orbit machining method according to the relatedart as is described above, no configuration that makes a cuttingvelocity constant has been adopted.

Patent Literature 2 discloses a configuration, for cutting method ofgear shaped object, needed to maintain a constant cutting velocity froma cutting start point to a cutting end point.

However, Patent Literature 2 only discloses that the cutting velocity ismade constant simply under the control of an NC lathe and fails toclarify what qualitative or quantitative criteria are used to make acutting velocity constant.

Patent Literature 3 discloses that a CAM controls the number ofrotations of the main shaft to obtain a constant cutting velocity.However, Patent Literature 3 also fails to clarify a specificconfiguration concerning what criteria are used to make a cuttingvelocity constant.

Furthermore, Patent Literatures 2 and 3 are predicted on cutting basedon rotation of the main shaft along a central shaft thereof and do notdisclose or suggest that the cutting velocity is constant when the mainshaft turns around a predetermined position serving as a center as isthe case with the present invention.

Thus, for the cutting of the inner circumferential face or the outercircumferential face of the work based on turning of the main shaft, nocutting method has been proposed in which the cutting velocity of thecutting tool is controlled to be constant.

RELATED ART LITERATURE Patent Literature

Patent Literature 1: JP H08-126938 A

Patent Literature 2: JP 2000-190126 A

Patent Literature 3: JP 2001-113443 A

BRIEF SUMMARY OF THE INVENTION

According to the present invention, there is provided a cutting methodin which, in cutting an inner circumferential face or an outercircumferential face of a work based on turning of a main shaft around apredetermined position serving as a center, control is enabled to make acutting velocity constant.

According to the present invention, there are further provided a basicconfiguration (1); a cutting method for an inner circumferential face oran outer circumferential face of a work using a cutting tool projectingfrom a main shaft which turns around a predetermined position serving asa center and for which a turning radius is adjustable, wherein, in thecase that a turning angular velocity of the main shaft is represented asω, a distance from a turning center to a tip of the cutting tool isrepresented as R, and a cutting velocity of the tip of the cutting toolis set to a constant value C, the cutting velocity of the cutting toolis made constant by performing control such that ω changes inassociation with a change in the distance R so that

$\omega = {\left( {C^{2} - {\overset{.}{R}}^{2}} \right)^{\frac{1}{2}}/R}$

is formulated (where R denotes a time differential of the distance R),and a basic configuration ({dot over (2)}) the cutting method for aninner circumferential face or an outer circumferential face of the workof the basic configuration (1), wherein a position of the turning centerof the main shaft is movable in an orthogonal direction or an obliquedirection to a plane orthogonal to the turning central axis, and whenthe position of the turning center of the main shaft is movable in theoblique direction, a supporting position of the work on a table on whichthe work is placed is also moved in association with the movement in theoblique direction to maintain a state where cutting is enabled.

In the aspect of the present invention, the basic configuration (1)makes a cutting velocity constant to provide an even cut face, while thebasic configuration (2) enables the inner circumferential face or theouter circumferential face of the work to be formed into any of variouscurved faces.

That is, the aspect of the present invention eliminates the need forcontrol based on complicated calculations or operations as disclosed inPatent Literature 2 and 3.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a system allowing a method of the presentinvention to be implemented;

FIGS. 2(a) and 2(b) are plan views denoting the state of a plane in adirection orthogonal to a turning central axis of a main shaft, FIG.2(a) denoting that an inner circumferential face is cut, and FIG. 2(b)denoting that an outer circumferential face is cut;

FIGS. 3(a) and 3(b) denote a method of forming a normal tapered shape bymoving the position of a turning center of the main shaft andsequentially changing a turning radius, FIG. 3(a) being a plan viewdenoting a locus of movement of a tip of a cutting tool, and FIG. 3(b)being a side view of the tapered shape formed by the sequential change;

FIGS. 4(a) and 4(b) denote a method of forming a stepped tapered shapeby moving the position of the turning center of the main shaft andchanging the turning radius in a stepwise manner, FIG. 4(a) being a planview denoting a locus of movement of the tip of the cutting tool, andFIG. 4(b) being a side view of the stepped tapered shape formed by thestepwise change; and

FIGS. 5(a), 5(b), and 5(c) are perspective views denoting a process offorming a ring shape by helically moving and finally circumferentiallymoving the tip of the cutting tool in an inner region and an outerregion of the work without moving the turning center position of themain shaft, FIG. 5(a) denoting a process of forming an inner wall in aring shape, FIG. 5(b) denoting a process of forming an outer wall in aring shape, and FIG. 5(c) denoting the finished ring shape.

DETAILED DESCRIPTION OF THE INVENTION

As is denoted in FIG. 1, components of the present invention include amain shaft 1 that turns, a cutting tool 2 provided at a tip side of themain shaft 1, a work 3, a table 4 that supports the work 3, and acontrol apparatus 5 that controls movement of the main shaft 1 and thetable 4 (in FIG. 1, blank arrows indicate a moving state of the mainshaft 1 associated with adjustment of a turning radius or a moving stateof the main shaft 1 in the orthogonal direction or the obliquedirection, curved arrows indicate a turning state by revolution of themain shaft 1 and a rotating state of the table 4, a dotted arrow fromthe control apparatus 5 indicates a state where signals which allow aturning angular velocity and a rotating angular velocity to becontrolled are dispatched, and solid arrows indicate states wheresignals are dispatched which allow control of movement of the main shaft1 associated with adjustment of the turning radius of the main shaft 1,and in the basic configuration (2), control of movement of the rotatingcenter of the table 4 associated with movement of the turning center ofthe main shaft 1 in the orthogonal direction or the oblique directionand movement of the turning center of the main shaft 1 in the obliquedirection).

In the present invention, elements to be controlled are parametersindicative of the turning angular velocity of the main shaft 1 withrespect to the turning center, and the turning radius of the main shaft1 (these elements correspond to the basic configuration (1)), andfurther the moving position and the moving velocity of the turningcenter in the orthogonal direction or the oblique direction with respectto a plane orthogonal to a central axis 6 for turning of the main shaft1 (the above-described elements correspond to the basic configuration(2)). For the basic configuration (1), the number of the parameters istwo, and for the basic configuration (2), the number of the parametersis three.

The main shaft 1 and the cutting tool 2 make turning motion around apredetermined central position. A tip of the cutting tool 2 cuts aninner circumferential face of the work 3 as is denoted in FIG. 2(a) orcuts an outer circumferential face of the work 3 as is denoted in FIG.2(b). The turning radius of the main shaft 1 from the central positionis adjustable, and thus, the radius of curvature of the tip of thecutting tool 2 is also adjustable, allowing a cutting curved face to beoptionally selected.

That is, circumferential curved faces in FIGS. 2(a) and 2(b) merelydenote typical examples based on rotation by the composition of therevolution of the main shaft 1 and the rotation of the table 4. Thecutting curved face is not necessarily limited to the circumferentialcurved face.

Criteria based on expressions for the basic configuration (1) andcorresponding to a technical demand for provision of an even cut facewill be described below.

As is denoted in FIGS. 2(a) and 2(b), if the distance from the turningcenter to the tip of the cutting tool 2 is represented as R, and anangular position of the cutting tool 2 is represented as θ, and that acoordinate position of the cutting tool 2 is represented as (X, Y), thenX=R cos θ and Y=R sin θ is formulated and

{dot over (X)}={dot over (R)} cos θ−R{dot over (θ)} sin θ,{dot over(Y)}={dot over (R)} sin θ+R{dot over (θ)} cos θ

is formulated (dots over reference characters indicate timedifferentials).

Therefore, when the cutting velocity is represented as V,

V ² ={dot over (X)} ² +{dot over (Y)} ² ={dot over (R)} ² +{dot over(R)} ²{dot over (θ)}²

is formulated.

According to the above-described relational expressions, wherein, in thecase that the turning angular velocity of the main shaft 1 isrepresented as ω₁ and the rotating angular velocity of the table 4 isrepresented as ω₂, the constant value C may be preset and controlled toformulate

$\omega = {\overset{.}{\theta} = {\left( {C^{2} - {\overset{.}{R}}^{2}} \right)^{\frac{1}{2}}/R}}$

in association with the distance R and {dot over (R)} that is a timedifferential of the distance R, in order to allow the tip of the cuttingtool 2 to operate at a constant cutting velocity V.

In the present invention, to form each of the inner and outercircumferential faces into any of various cutting shapes, the followingembodiment may be adopted. That is, as shown in the basic configuration(2), the position of the turning center of the main shaft 1 is movablein an orthogonal direction or an oblique direction to the planeorthogonal to the turning central axis 6. When the position of theturning center of the main shaft 1 is movable in the oblique direction,a supporting position of the work 3 on the table 4 on which the work 3is placed is also moved in association with the movement in the obliquedirection to maintain a state where cutting is enabled.

When the turning center of the main shaft 1 is movable in the obliquedirection as is described above, the turning central axis 6 of the mainshaft 1 moves by itself. Thus, the supporting position of the work 3 onthe table 4 on which the work 3 is placed is forced to move withsynchronized state to the position of the turning center in order tomaintain a state where the cutting tool 2 can cut the work 3.

FIGS. 3(a) and 3(b) denote that the outer circumferential face is formedinto a normal tapered shape in accordance with the embodiment in whichthe position of the turning center of the main shaft 1 is moved in theorthogonal direction or the oblique direction, while the turning radiusis sequentially changed.

When the tapered shape has circumferential curved faces at opposite endsthereof, the turning radius may be approximately constant at an initialstage and a final stage of turning as is denoted in FIGS. 3(a) and 3(b).

FIGS. 4(a) and 4(b) denote that the inner circumferential face is formedinto a stepped tapered shape in accordance with the embodiment in whichthe position of the turning center of the main shaft 1 is moved in theorthogonal direction or the oblique direction, while the turning radiusis changed in a stepwise manner.

As is apparent from FIGS. 3(a) and 3(b) and FIGS. 4(a) and 4(b), thebasic configuration (2) enables the inner circumferential face or theouter circumferential face to be formed into any of various shapes.

The above-described drawings all denote that the turning center of themain shaft 1 is moved in the direction orthogonal to the planeorthogonal to the turning central axis 6, that is, in the same directionas that of the turning central axis 6. When the turning center is movedin the direction oblique to the plane, a tapered shape is obtained whichgenerally changes in the oblique direction.

Alternatively to the embodiments denoted in FIGS. 3(a) and 3(b) andFIGS. 4(a) and 4(b), if the turning radius of the main shaft 1 is notchanged, the inner circumferential face or the outer circumferentialface (not denoted in the drawings) can be formed into a normalcylindrical shape (when the turning center moves in the orthogonaldirection) or an oblique cylindrical shape (when the turning centermoves the in the oblique direction).

FIG. 5 denotes an embodiment in which the position of the turning centerof the main shaft 1 is not moved in the orthogonal direction nor theoblique direction. In the embodiment, a ring shape is formed as follows:

(1) In an inner region of the work 3 that is close to the turningcenter, the distance from the turning center to the tip of the cuttingtool 2 is sequentially increased to move the tip along a helical locus,in the case that the distance reaches a maximum state, the maximum stateis maintained to form an inner wall in a ring shape.(2) In an outer region of the work 3 that is away from the turningcenter, the distance from the turning center to the tip of the cuttingtool 2 is sequentially reduced to move the tip along a helical locus, inthe case that the distance reaches a minimum state, the minimum state ismaintained to form an outer wall in a ring shape.

In the above-described embodiment, the ring shape can be quicklyobtained.

Thus, in the present invention, the work 3 is cut with a summation ofthe cutting velocity to allow the inner circumferential face and theouter circumferential face to be quickly formed. The need for specialcontrol for the summation is not required to achieve simple control.

Example

In an example, a plurality of main shafts 1 and cutting tools 2projecting from the respective main shafts 1 are adopted.

In this example, the plurality of cutting tools 2 performs cutting tofurther increase the cutting velocity, while the properties of theindividual cutting tools 2 related to the cut face are averaged to allowa more even cut face to be provided.

As is described above, the present invention enables the innercircumferential face and the outer circumferential face of the work tobe cut into any of various shapes with even cut faces at a constantcutting velocity. Thus, the present invention has enormousapplicability.

1. A cutting method for an inner circumferential face or an outercircumferential face of a work using a cutting tool projecting from amain shaft which turns around a predetermined position serving as acenter and for which a turning radius is adjustable, comprising the stepof: in the case that a turning angular velocity of the main shaft isrepresented as ω, a distance from a turning center to a tip of thecutting tool is represented as R, and a cutting velocity of the tip ofthe cutting tool is set to a constant value C, making the cuttingvelocity of the cutting tool constant by performing control such that ωchanges in association with a change in the distance R so that$\omega = {\left( {C^{2} - {\overset{.}{R}}^{2}} \right)^{\frac{1}{2}}/R}$is denoted (where {dot over (R)} denotes a time differential of thedistance R).
 2. The cutting method for an inner circumferential face oran outer circumferential face of a work according to claim 1, wherein aposition of the turning center of the main shaft is movable in one of:an orthogonal direction and an oblique direction to a plane orthogonalto the turning central axis, and when the position of the turning centerof the main shaft is movable in the oblique direction, moving asupporting position of the work on a table on which the work is placedin association with the movement in the oblique direction to maintain astate where cutting is enabled.
 3. The cutting method for an innercircumferential face or an outer circumferential face of a workaccording to claim 2, further comprising the step of moving the positionof the turning center of the main shaft in one of the orthogonaldirection and the oblique direction, while the turning radius issequentially changed.
 4. The cutting method for an inner circumferentialface or an outer circumferential face of a work according to claim 2,further comprising the step of moving the position of the turning centerof the main shaft in one of the orthogonal direction and the obliquedirection, while the turning radius is changed in a stepwise manner. 5.The cutting method for an inner circumferential face or an outercircumferential face of a work according to claim 1, wherein a positionof the turning center of the main shaft is not moved in the orthogonaldirection nor the oblique direction, and further comprising the step offorming a ring shape by the following steps: (1) in an inner region ofthe work that is close to the turning center, sequentially increasingthe distance from the turning center to the tip of the cutting tool tomove the tip along a helical locus, in the case that the distancereaches a maximum state, so that the maximum state is maintained to forman inner wall in a ring shape, and (2) In an outer region of the workthat is away from the turning center, sequentially reducing the distancefrom the turning center to the tip of the cutting tool to move the tipalong a helical locus, in the case that the distance reaches a minimumstate, so that the minimum state is maintained to form an outer wall ina ring shape.
 6. The cutting method for an inner circumferential face oran outer circumferential face of a work according to claim 1, furthercomprising the step of adopting a plurality of main shafts and cuttingtools projecting from the respective main shafts.